Traditionally, meat is visually inspected and graded after an animal has been slaughtered. With beef, for example, a cut is made between the 12th and 13th rib. A grader then visually inspects the exposed meat. Based on the appearance of this cross section, the grader classifies the meat according to predetermined standards that reflect the amount of fat, or marbling, present in the meat. Typically, beef is classified according to U.S. Department of Agriculture (USDA) guidelines. Under USDA guidelines, meat can be classified as standard, select, choice or prime.
The visual inspection of meat has several disadvantages. First, the grading is subjectively based on the opinion of the grader. Different graders may assign different grades to the same piece of meat. Even the same grader might assign different grades to the same meat on different days. This is extremely important because the value of the meat is directly dependent on the grade it is assigned.
Visual grading of meat is also limited because the grader only has access to an area of the meat exposed at the cut. Generally, this grading is based solely on the quality of the meat at the cut between the 12th and 13th ribs. If that area does not accurately reflect the entire side of meat, the grade assigned to the meat will be incorrect.
Moreover, traditional techniques only provide information based on what is visually apparent to the grader. While the grader can visually estimate the marbling of the beef there is no way for him to determine the flavor and tenderness, or "merit," of the meat. This is important because one out of four sides of beef classified as "prime" is still rejected as unsatisfactory by discriminating customers, such as restaurants specializing in beef steak.
The traditional method obviously cannot be used to grade the quality of live cattle. Knowing exactly when to slaughter cattle is important to maximize profits. Ranchers send herds of cattle to feed lots prior to processing. The feed lots attempt to create the highest quality meat at the lowest cost. Currently, feed lots must estimate when an entire group, or pen, of cattle has been sufficiently fed. A pen might contain 50, 100, or even 150 head of cattle. If the cattle have not been fed long enough the quality of the meat, and its value, suffers. On the other hand, if the cattle are fed too long the increase in the quality of the meat will not justify the extra expense of feeding the animals plus a reduced grade penalty. Because there is no way to determine the quality of live cattle, an owner can only estimate the point of maximum profitability for a particular animal. For example, feed lot operators generally hold all pens a fixed number of days selected to maximize profits. Even with this approach, however, about one third of the individual animals in any given pen are under-fed and one third are over-fed. It would be desirable to know the quality of each animal in the pen so every animal can be processed at the peak of its profitability.
Because the traditional technique can only be used on slaughtered animals, it is of limited use when attempting to breed a more profitable herd. If the cattle owner had instant feedback about the quality of the animals in the herd, higher quality animals could be selected for breeding. This would improve the genetic quality of the herd over time. Currently, the cattle owner must wait until an animal has left the feed lot and been slaughtered before any decisions about the genetic quality of the animal can be made.
The lack of instant feedback also prevents a cattle owner from responding to changes in consumer preferences. If consumers begin to demand leaner meat, for example, the cattle owner cannot make decisions about a herd until each animal has left the feed lot and has been slaughtered. This process can take up to six months or more.
To overcome some of these limitations, ultrasound technology has been used for the last two decades in animal research and applications. Ultrasound scanning technology utilizes high frequency sound waves to collect information from live tissue in a non-invasive manner. Efforts in the ultrasonic measurement of meat have concentrated on the use of real-time "B" mode imaging. B mode ultrasound, often used in medical applications, provides the operator with a two dimensional picture of the tissue being inspected. Brightness and texture are used in the image to characterize the animal's muscle tissue. By studying the two-dimensional image, the operator can characterize the muscle tissue and grade the animal. This approach, however, suffers from the same limitation as the traditional method because it is still based on the subjective opinion of the operator. Additionally, operators must be highly trained to interpret the B mode images correctly.
There have been attempts to mechanize and computerize the use of B mode imaging. Obtaining accurate measurements of these tissue characteristics is difficult because of speckle noise present in the image. Moreover, B mode imaging equipment is extremely expensive and transducers used with B mode imaging quickly wear out when used on rough surfaces, such as the hide of an animal Equipment used with B mode imaging is also very large and does not lend itself to use in the field. Finally, B mode imaging is not able to determine the flavor and tenderness, or "merit," of the meat.